This application is based upon application No. 2000-280288 filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a drive mechanism employing an electromechanical transducer. More specifically, the present invention relates to the drive mechanism employing the electromechanical transducer or vibrating member, suitable for actuating a moving body equipped in an apparatus such as a precise device and a high-technology info tool, and for adapting a microactuator for minute operation.
2. Description of the Related Arts
Conventionally, there have been proposed some drive mechanisms employing electromechanical transducers. For example, in a drive mechanism as shown in FIG. 11, a moving body 51 contacts frictionally with a drive rod 53, which is movably supported by stationary plates 62 and 63. One end of the piezoelectric element 58 is fixed to the stationary plate 64, and its opposite end is fixed to one of the ends of the drive rod 53. In the arrangement, the piezoelectric element 18 expands at a first velocity and contracts at a second velocity, different from the first velocity, when the piezoelectric element 18 is supplied with drive pluses, for example, having a saw-teeth-shaped waveform. Thereby the drive rod 53 moves and the moving body 51 is driven along the drive rod 53 (See, for example, Japanese Non-examined Patent Publication No. 7-274544).
However, the strength of the piezoelectric element is low. Therefore, it is necessary to protect the piezoelectric element 58 from the excessive force.
Specifically, it is necessary to complicate the construction of the drive mechanism, and to limit the drive condition such as the drive velocity and the load, in order to prevent the external force from causing bending moment, torsion torque, compressive force, and tensile force to the piezoelectric element.
Additionally, it is necessary that expanding and contracting direction of the piezoelectric element 58 is precisely coincident with moving direction of the drive rod 53 moves. Therefore, it is difficult to assemble the drive mechanism, due to close tolerance of positioning the piezoelectric element 58 and drive rod 53.
Moreover, the method for fixing the piezoelectric element 58 must be chosen from methods, in which no excessive force is exerted on the piezoelectric element 58. The drive mechanism must be assembled without exerting the excessive force on the piezoelectric element 58. Thus, it is difficult to assemble the drive mechanism efficiently.
Accordingly, it is an object of the present invention to provide a drive mechanism employing an electromechanical transducer, on which no excessive force is exerted.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a drive mechanism, comprising: a stationary member; a drive member fixed to the stationary member; an electromechanical transducer fixed to the drive member; and a driven member which is driven by the drive member and which contacts frictionally with the drive member under a predetermined frictional force exerting therebetween, wherein the electromechanical transducer is supplied with drive pulses, so that the electromechanical transducer expands at a first velocity and contracts at a second velocity, different from the first velocity, and so that the driven member moves along the drive member in a predetermined direction.
In the construction, the electromechanical transducer (for example, electrostatic actuator, piezoelectric transducer, electrostriction transducer, magnetostriction transducer, and so on) changes the electrical energy (for example, electric voltage, electric current, electric field, electric charge, static electricity, magnetic field) supplied thereto into the mechanical energy (for example, transformation or strain such as prolonging, compressing, expanding, contracting, bending, twisting).
In the construction, even though the principle of driving is not completely clear, the driven member can be driven relative to the drive member in a predetermined direction, by means of supplying appropriate drive pulses, for example, having a saw-teeth-shaped waveform. Such drive pulses causes the transformation of the electromechanical transducer, so that the drive member vibrates with mutually different velocities, even if the drive member is fixed to the stationary member. Namely, the vibration of the drive member includes one component at relatively slow velocity proceeding in one direction, and the other component at relatively fast velocity proceeding in opposite direction. We reason; that the one component of the vibration does not cause the relative sliding between the drive member and the driven member; that the other component of the vibration causes the relative sliding therebetween; and that by repeating such a cycle, the driven member can be driven relative to the drive member in a predetermined direction.
In the construction, the electromechanical transducer is fixed to (or restrained by) only the drive member, and thereby, no excessive force is exerted on the electromechanical transducer.
As an embodiment, expansion and contraction of the electromechanical transducer makes the drive member vibrate, so that a cycle of the vibration of the drive member causes one state in which the driven member slides along (or is slidable along) the drive member in a predetermined direction, resisting the frictional force exerting therebetween, and another state in which the driven member does not slide along (or is unslidable along, or remains stationary against) the drive member with the frictional force exerting therebetween.
As an embodiment, the drive member has a pair of ends, so that a portion near one of the ends of the drive member is fixed to the stationary member, and so that the electromechanical transducer is fixed to the other of the ends of the drive member.
According to the embodiment, it is possible to prevent the drive member from moving, and to have a driving range of the driven member along the drive member between one positions fixed to the stationary member and the other position fixed to the electromechanical transducer, without any stopper for preventing the driven member from moving beyond the driving range.
As an embodiment, the drive member has a pair of ends, so that a portion near one of the ends of the drive member is fixed to the stationary member, and so that the electromechanical transducer is fixed to the one of the ends of the drive member.
According to the embodiment, it is possible to increases the space around the driven member.
As an embodiment, another portion near the other of the ends of the drive member is supported by the stationary member.
According to the embodiment, it is possible to prevent the drive member from moving, and to have a driving range of the driven member along the drive member between one position fixed to the stationary member and the other position supported by the stationary member, without any stopper for preventing the driven member from moving beyond the driving range.
As an embodiment, another portion near the other of the ends of the drive member is fixed to the stationary member.
According to the embodiment, it is possible to prevent the drive member from moving, and to have a driving range of the driven member along the drive member between two positions fixed to the stationary member, without any stopper for preventing the driven member from moving beyond the driving range.
As an embodiment, the stationary member is fixed to a lens barrel, and wherein the driven member holds a lens.
As an embodiment, the drive member is fixed to the stationary member by one of caulking, press fitting, fusion bonding, adhesive bonding, screw fastening, and welding.
As an embodiment, the drive member is formed with elastic material.
In order to achieve the above object, according to another aspect of the present invention, there is provided a drive mechanism, comprising: a stationary member; a drive member, having a pair of ends, fixed to the stationary member; a first electromechanical transducer fixed to one of the ends of the drive member; a second electromechanical transducer fixed to the other of the ends of the drive member; and a driven member which is driven by the drive member and which contacts frictionally with the drive member under a predetermined frictional force exerting therebetween, wherein at least one of the first electromechanical transducer and the second electromechanical transducer is supplied with drive pulses, so that the at least one thereof expands at a first velocity and contracts at a second velocity, different from the first velocity, and so that the driven member moves along the drive member in a predetermined direction.
In the construction, the electromechanical transducers are fixed to (or strained by) only both ends of the drive member, and thereby, no excessive force is exerted on the electromechanical transducers.
Moreover, in the construction, it is possible to drive the driven member identically in one direction and opposite direction, for example, by supplying same drive pulses to either one of the electromechanical transducers selectively.
As an embodiment, expansion and contraction of the at least one of the first electromechanical transducer and the second electromechanical transducer makes the drive member vibrate, so that a cycle of the vibration of the drive member causes one state in which the driven member slides along (or is slidable along) the drive member in a predetermined direction, resisting the frictional force exerting therebetween, and another state in which the driven member does not slide along (or is unslidable along, or remains stationary against) the drive member with the frictional force exerting therebetween.
As an embodiment, a portion near the one of the ends of the drive member and another portion near the other of the ends thereof are fixed to the stationary member.
According to the embodiment, it is possible to prevent the drive member from moving, and to have a driving range of the driven member along the drive member between two positions fixed to the stationary member, without any stopper for preventing the driven member from moving beyond the driving range.
As an embodiment, the stationary member is fixed to a lens barrel, and wherein the driven member holds a lens.
As an embodiment, the drive member is fixed to the stationary member by one of caulking, press fitting, fusion bonding, adhesive bonding, screw fastening, and welding.
As an embodiment, the drive member is formed with elastic material.
In order to achieve the above object, according to still another aspect of the present invention, there is provided a drive mechanism, comprising: a first member; a second member for contacting frictionally with the first member under a predetermined frictional force exerting therebetween; and an electromechanical transducer fixed to the first member, wherein the electromechanical transducer is supplied with drive pulses, so that the electromechanical transducer expands at a first velocity and contracts at a second velocity, different from the first velocity, and so that one of the first member and the second member moves relative to the other thereof in a predetermined direction.
In the construction, the electromechanical transducer vibrates the first member with mutually different velocities. Namely, the vibration of the first member includes one component at relatively slow velocity proceeding in one direction, and the other component at relatively fast velocity proceeding in opposite direction. The one component of the vibration does not cause the relative sliding between the first member and the second member. On the other hand, the other component of the vibration causes the relative sliding therebetween. By repeating such a cycle, in case that one of the first member and the second member is fixed to the stationary member, the other thereof is driven relative to the one thereof in a predetermined direction.
In the construction, the electromechanical transducer is restrained by only the first member, and thereby, it is possible to exert no excessive force on the electromechanical transducer.
As an embodiment, expansion and contraction of the electromechanical transducer makes the first member vibrate, so that a cycle of the vibration of the first member causes one state in which the one of the first member and the second member moves along (or is movable along) the other thereof in a predetermined direction, resisting the frictional force exerting therebetween, and another state in which the one thereof does not move along (or is unmovable along, or remains stationary against) the other thereof with the frictional force exerting therebetween.
In order to achieve the above object, according to still another aspect of the present invention, there is provided a drive mechanism, comprising: a stationary member; a first drive member fixed to the stationary member; a first electromechanical transducer fixed to the fist drive member; a first driven member which is driven by the first drive member and which contacts frictionally with the first drive member under a predetermined frictional force exerting therebetween; a second drive member fixed to the first driven member; a second electromechanical transducer fixed to the second drive member; a second driven member which is driven by the second drive member and which contacts frictionally with the second drive member under a predetermined frictional force exerting therebetween; a third drive member fixed to the second driven member; a third electromechanical transducer fixed to the third drive member; a third driven member which is driven by the third drive member and which contacts frictionally with the third drive member under a predetermined frictional force exerting therebetween, wherein each of the first electromechanical transducer, the second electromechanical transducer, and the third electromechanical transducer is supplied with drive pulses, so that each thereof expands at a first velocity and contracts at a second velocity, different from the first velocity, respectively, and so that each of the first driven member, the second driven member, and the third driven member moves relative to each of the first drive member, the second drive member, and the third drive member in a predetermined direction, respectively.
In the construction, the third driven member can be driven at three or more degrees of freedom in three-dimensional space.
As an embodiment, expansion and contraction of each of the first electromechanical transducer, the second electromechanical transducer, and the third electromechanical makes each of the first drive member, the second drive member, and the third drive member vibrate respectively, so that a cycle of the vibration of each thereof causes one state in which each of the first driven member, the second driven member, and the third driven member moves along (or is movable along) each of the first drive member, the second drive member, and the third drive member in a predetermined direction, resisting the frictional force exerting therebetween, respectively, and another state in which each of the first driven member, the second driven member, and the third driven member does not move along (or is unmovable along, or remains stationary against) each of the first drive member, the second drive member, and the third drive member with the frictional force exerting therebetween, respectively.
As an embodiment, the first drive member, the second drive member, and the third drive member are arranged, so that the moving directions of the first driven member, the second driven member, and the third driven member are substantially perpendicular to each other.
In the construction, the vibration in one of the driven members exerts no influence on the other thereof, and therefore the drive mechanism can be driven efficiently.